Must be installed to protect impeller from damage due to any foreign objects that might be in solution when CPVC pump is used strictly for agitation (without filter cartridge attached). Fits BX650, BX1200, BX3000, BX5000, BXL2500 & BXL5000. 2-3/8" outside diameter (6 cm) x 2-1/4" long (5.71 cm).